1. Field of the Invention
This invention relates in general to seismic pulsing devices and in particular to seismic pulsing devices for use in boreholes to create seismic pulses.
2. Description of the Prior Art
The use of seismic waves to determine the geophysical and geological structure and characteristics of a subterranean region is well known. In a typical application, sonic wave detectors, or seismometers, are arranged on the surface above the region to be explored. A seismic source is triggered to emit one or a series of seismic pulses. The array of seismometers arranged at the surface detects pulses passing through the earth formations. Typically, this procedure is not performed while drilling a well for oil or gas, but instead is used in earlier exploration programs to find the best location for drilling a well.
An example of a seismic data gathering system which is employed while drilling an oil or gas well is shown in U.S. Pat. No. 4,207,619, issued on Jun. 10, 1980 to Alf Klaveness. The '619 patent teaches using any suitable seismic pulse generator placed in the drill string near the drill bit and advanced in the well together with the drill bit to generate seismic pulses at any depth and without the need to remove the drill string and thus interrupt drilling operations. Sensors spaced laterally from the drilling rig detect the seismic pulses.
Seismic pulse generators for use with drill strings are shown in prior patents, however, they are not in commercial use. A need exists for a robust pulse generator that is simple to operate, that functions effectively under various drilling conditions, and generates omni-directional seismic pulses of suitable force and frequencies to delineate geologic structure around and below the borehole to distances of 4,000 feet or more. A need also exists for a pulse generator having the above qualities that can also be operated without substantial interruption of, or hindrance to, the drilling operations.